Peterson M E, Melián C, Nichols R
Caspary Research Institute and the Bobst Hospital of the Animal Medical Center, New York, NY 10021, USA.
J Am Vet Med Assoc. 2001 Feb 15;218(4):529-36. doi: 10.2460/javma.2001.218.529.
To determine the usefulness of measuring serum free thyroxine (T4) concentration as a diagnostic test for hyperthyroidism in cats, and to determine the influence of nonthyroidal disease on free T4 concentration in cats without hyperthyroidism.
Prospective case series.
917 cats with untreated hyperthyroidism, 221 cats with nonthyroidal disease, and 172 clinically normal cats.
Serum free T4, total T4, and total triiodothyronine (T3) concentrations were measured in cats with untreated hyperthyroidism and cats with nonthyroidal disease. Serum total T4 and T3 concentrations were determined by use of radioimmunoassay, and free T4 concentration was measured by use of direct equilibrium dialysis. Reference ranges for hormone concentrations were established on the basis of results from the 172 clinically normal cats.
Sensitivity of serum free T4 concentration as a diagnostic test for hyperthyroidism was significantly higher than the test sensitivity of either total T4 or T3 concentration. Of the 221 cats with nonthyroidal disease, 14 had a high free T4 concentration (ie, false-positive result). Therefore, calculated specificity of measuring serum free T4 concentration as a diagnostic test for hyperthyroidism was significantly lower than test specificity of measuring either the total T4 or T3 concentration.
Results indicate that determination of free T4 concentration is useful in the diagnosis of hyperthyroidism, especially in cats in which hyperthyroidism is suspected but total T4 and T3 concentrations are within reference ranges. However, because some cats with nonthyroidal disease have high serum free T4 concentrations, hyperthyroidism should not be diagnosed solely on the finding of high free T4 concentration.
确定测量血清游离甲状腺素（T4）浓度作为猫甲状腺功能亢进症诊断试验的效用，并确定非甲状腺疾病对无甲状腺功能亢进症猫的游离T4浓度的影响。
前瞻性病例系列。
917只未经治疗的甲状腺功能亢进症猫、221只患有非甲状腺疾病的猫和172只临床正常的猫。
测量未经治疗的甲状腺功能亢进症猫和患有非甲状腺疾病的猫的血清游离T4、总T4和总三碘甲状腺原氨酸（T3）浓度。血清总T4和T3浓度采用放射免疫测定法测定，游离T4浓度采用直接平衡透析法测定。根据172只临床正常猫的结果建立激素浓度的参考范围。
血清游离T4浓度作为甲状腺功能亢进症诊断试验的敏感性显著高于总T4或T3浓度的试验敏感性。在221只患有非甲状腺疾病的猫中，有14只的游离T4浓度较高（即假阳性结果）。因此，计算得出的测量血清游离T4浓度作为甲状腺功能亢进症诊断试验的特异性显著低于测量总T4或T3浓度的试验特异性。
结果表明，测定游离T4浓度对甲状腺功能亢进症的诊断有用，尤其是在怀疑患有甲状腺功能亢进症但总T4和T3浓度在参考范围内的猫中。然而，由于一些患有非甲状腺疾病的猫血清游离T4浓度较高，不应仅根据游离T4浓度升高就诊断为甲状腺功能亢进症。
